A conventional electroconductive contact unit for use in contact probes for electrically testing conductor patterns of printed circuit boards and electronic devices typically comprises an electroconductive needle member and a tubular holder that receives the needle member in an axially moveable manner, and the needle member is resiliently urged by a coil spring in the direction to project the tip of the needle member from the front end of the holder so that the tip of the needle member may be resiliently brought into contact with an object to be tested.
Silicon wafers and ceramic packages for use with semiconductor devices and glass panels for use in LCD panels are made of materials having a relatively high hardness. These components are provided with electric circuitry, and are subjected to electric testing during the manufacturing process. An electroconductive contact unit (contact probe) is used for such a purpose, and is adapted to establish electric contact with a part of the circuitry such as a terminal.
One form of such tests is the wafer level test (WLT), and noble metal alloys are sometimes used for the needle member of an electroconductive contact unit for use in such a test. Paliney 7 (tradename of The J. M. Ney Company of Bloomfield, Conn.) is one of such noble metal alloys, and is highly electroconductive, hard and wear resistant for a noble metal alloy, and resistant to surface oxidization so that the contact resistance would not increase for an extended period of time. An electroconductive contact unit using an electroconductive needle member made of this material is suitable for testing a device via a solder ball.
When a needle member is applied repeatedly to solder balls, solder inevitably deposits on the contact surface of the needle member over time. Such a soiled contact surface can be renewed to an original state by grinding the surface when the needle member is made of a noble metal alloy. On the other hand, when the needle member is made of SK material (carbon tool steel) and is provided with a plated surface, grinding of the contact surface only exposes the material of the needle member, and the original electric property cannot be regained.
A needle member made of a noble metal alloy such as Paliney 7 demonstrates a high electroconductivity, but is not so favorable as that of a needle member made of gold or plated with gold. As the performance of the semiconductor products becomes higher, the electric properties of the existing needle member made of a noble metal alloy are found to be more and more unsatisfactory. By increasing the thickness of the gold plated layer, the needle member can be ground and renewed for an increased number of times before the material of the needle member is exposed. However, increasing the thickness of the gold plated layer increases the manufacturing cost of the needle member, and the needle member cannot be ground not so many times as desired.